Process for treating continuously cast material



June 29, 1965 1:. A. OLSSON I 3,

PROCESS FOR TREATING CONTINUOUSLY CAST MATERIAL Filed Aug. 16, 1962 G O W ERM A. OLSSON ATTORNEY$ United States Patent i 3,191,251 PROCESS FOR TREATING CONTINUOUSLY CAST MATERIAL Erik Allan Olsson, Ziirichstrasse 66, Kusnacllt, Zurich, Switzerland Filed Aug. 16, 1962, Ser. No. 217,330 2 Claims. (Cl. 22-2001) In the continuous casting of metals, iron and steel for example, the melt passes through an open-ended mould which is ordinarily water-cooled from which the at least partially solidified emerging ingot or casting is withdrawn continuously or intermittently. Thereafter the casting can pass through a direct-cooling zone usually comprising a direct water spray. The cooling zone is preferably positioned before the withdrawal device so that the casting will have time to solidify sutficiently, so that the withdrawal device, when exerting a sufiicient pressure to get a firm grip, can grip and move the strand without deforming it.

Especially when casting iron and steel the temperature of the casting is fairly high, ordinarily more than 1000 C. and as a result the casting immediately oxidizes upon contacting oxygen in the air. In the cooling zone the oxidation of the casting surface is to some extent diminished by the coolingetfect of the water spray and since the scale which nonetheless forms is immediately flushed away from the surface, the casting usually appears to leave the cooling zone entirely free of scale. The higher the temperature of the casting after emerging from the cooling zone or the higher its temperature due to reheating of the surface layer, the faster the surface becomes coated with scale. Sometimes the oxidizing influence of the air causes a decarbu-rized surface layer to form, a risk which is especially in evidence when casting high carbon steel grades, for example valve spring steel.

Only in exceptional cases is the casting rolled directly at casting heat. Ordinarily the casting is, instead after cooling and possibly after a surface inspection, reheated to rolling temperature, thus permitting fresh scale to form and causing risk of decarburizing. Therefore, especially when certain high carbon steel grades are rolled it is necessary to keep the atmospheric conditions in the reheating furnace under careful control. By making use of resistance heating the possibilities of reducing said risks have been improved significantly, but obviously a great deal would be gained if this problem were solved more completely.

This invention comprises a process to reduce scale formation and the tendency to carburize both in connection with casting and with subsequent heating of ingots for continued rolling. Furthermore the invention is intended to provide a possiblity to affect the surface layer in regard to its chemical composition, by carburizing, for example. For this latter purpose it is proposed, in accordance with this invention, that the casting shall be provided, immediately adjecent to the casting process, with a surface coating of a chemically active and/or non-scaling substance.

The invention is further clarified by the following, which refers to the appended drawing showing schematically a machine for the continuous casting of metals, provided with devices to give a coating to the continuously cast material.

The drawing shows a machine for continuous casting of metals comprising a ladle from which the molten metal is poured into a tundish 11 which is provided with a bottom hole through which the molten metal is poured to an open-ended mould 12 which is cooled, by water for example, by a method not shown. The casting 13 is withdrawn from the mould 12 by power rolls 14. Immediately after the mould 12 the casting 13 passes a cooling zone 14 in which cooling is accomplished by a direct water spray which is supplied by two water feed pipes 15 and 16 and sprayed against the casting 13 through several nozzles 17 positioned at a distance from each other along the length of the casting. In the cooling zone 14 the casting is guided by means of several rolls 18. The cooling zone 14 is enclosed in a housing 19 with a discharge opening 20 for steam and a lower drain 21 for cooling water which has not vaporized. A hose or pipeline 22 can be connected to housing 19 to supply an inert gas and/ or a reducing agent.

This invention provides for a device immediately beneath the cooling zone 14 which gives the casting a surface coating. In the particular case described here, sprayers 23, 24 spray a substance which is suspended in a liquid and which sinters and/ or melts when it contacts the hot surface of the casting. It should be mentioned that the temperature of the casting immediately after the cooling zone 14 when metals, iron and steel, for example, are cast continuously often remains above 900 C.

In this particular case the sprayers 23, 24 are supplied with a substance suspended in a liquid through hoses or a pipeline 25 while compressed air is supplied through hoses or a pipeline 26. Naturally other methods can be used instead of spraying, as the composition and consistency of the surface coating may demand.

The surface coating could be compounds resembling glass or enamel, certain blends of clay, etc. Such materials can also be used as carrier for other additives required by the process.

In certain cases one or more films of a metal or metal alloy can be applied as coating, for example aluminum or an alloy of aluminum. In such case it is suitable to apply the film by flame spraying.

Th substance used for coating should, of course, have sufiicient strength and toughness to withstand continued cooling, handling and reheating. Preferably, a substance should be used which can be removed by spraying with water under pressure, which ordinarily takes place when scale is removed for rolling.

Modifications and changes in detail can be made within the scope of this inventive concept.

I claim:

1. Process for continuously and simultaneously casting and coating a ferrous, or like high temperature, metal which comprises the steps of feeding molten ferrous metal into a mold open at both ends, withdrawing a metal ingot from the mold, applying a cooling liquid to said ingot in a cooling zone immediately adjacent the discharge end of the mold to cool the ingot to a temperature above 900 C., and coating said ingot with a material selected from the group consisting of glass, enamel and clay and suspended in a liquid to prevent oxidizing and decarburizing in a coating zone immediately following the cooling zone.

2. Process as in claim 1, wherein said coating step comprises spraying said material on to the moving ingot.

References Cited by the Examiner UNITED STATES PATENTS 2,657,457 11/53 Toulmin 117-107.1 2,816,826 12/57 Brennan 22200.1 2,824,346 2/58 Osborn 22200.1 2,858,586 11/58 Brennan 22200.1 2,881,518 4/59 Toulmin 117-107.1 2,887,984 5/59 Dummond 1 17107 .1 2,955,334 10/60 Pulsifer 22--200.1

FOREIGN PATENTS 823,323 12/51 Germany.

MARCUS U. LYONS, Primary Examiner.

MICHAEL V. BRINDISI, Examiner. 

1. PROCESS FOR CONTINUOUSLY AND SIMULTANEOUSLY CASTING AND COATING A FERROUS, OR LIKE HIGH TEMPERATURE, METAL WHICH COMPRISES THE STEPS OF FEEDING MOLTEN FERROUS METAL INTO A MOLD OPEN AT BOTH ENDS, WITHDRAWING A METAL INGOT FROM THE MOLD, APPLYING A COOLING LIQUID TO SAID INGOT IN A COOLING ZONE IMMEDIATELY ADJACENT THE DISCHARGE END OF THE MOLD TO COOL THE INGOT TO A TEMPERATURE ABOVE 900*C., AND COATING SAID INGOT WITH A MATERIAL SELECTED FROM THE GROUP CONSISTING OF GLASS, ENAMEL AND CLAY AND SUSPENDED IN A LIQUID TO PREVENT OXIDIZING AND DECARBURIZING IN A COATING ZONE IMMEDIATELY FOLLOWING THE COOLING ZONE. 